New surfer still having trouble..

I'm going to try to keep this relatively short and to the point.
I got a 6'8 fish as my first board, I started surfing in south florida (The swell is not very nice or reliable, but we make it work).
Weeks of practice and I've come to this: The board floats me okay, Is very quick, is very unstable for me.
I went out with a friend on his 7'4 longboard and he let me use it and wow, it was really nice. Things I noticed about his board: His board floated me very well, it felt slow
, is very stable.
On my fish, I would always have problems popping up due to the instability and my lack of pop up form. On his board (despite it feeling slower), it was nice because I could pop up slowly and not fall off the board.
My point / question:
Is there a board size that will give me the speed of the fish, with the stability of the longboard? I'm thinking a 7'2 fish or 7'2 longboard?
(it perplexes me how 8 inches can make so much of a difference)
Thanks for any input!
I got a 6'8 fish as my first board, I started surfing in south florida (The swell is not very nice or reliable, but we make it work).
Weeks of practice and I've come to this: The board floats me okay, Is very quick, is very unstable for me.
I went out with a friend on his 7'4 longboard and he let me use it and wow, it was really nice. Things I noticed about his board: His board floated me very well, it felt slow

On my fish, I would always have problems popping up due to the instability and my lack of pop up form. On his board (despite it feeling slower), it was nice because I could pop up slowly and not fall off the board.
My point / question:
Is there a board size that will give me the speed of the fish, with the stability of the longboard? I'm thinking a 7'2 fish or 7'2 longboard?
(it perplexes me how 8 inches can make so much of a difference)
Thanks for any input!